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This file contains 2 supplementary tables. The first table is the temperature conditions of the temperature of the ten temperature baths used during the full experimental period . The second table is tThe thermal optimum range (Topt) with survival ≥ 75%, lower and upper temperatures with >50% mortality (LT50) in A. lixula after 24 and 48 hours for all crosses and populations.

Amphiglena aeoliensis sp. nov. (Figs 18, 19) Material examined. Holotype (MNCN 16.01 /18913): Italy: Panarea Island (Aeolian Archipelago), near the Bottaro crater, 27 September 2016, 8 m depth; station B2, 38°38’14.49”N 15° 6’34.47”E). Paratypes: MNCN 16.01 /18914: 8 specimens from the same locality and date as the holotype; PCZL: 19 specimens B2 site, 27 September 2016; PCZLS.A. 9.1. 79 specimens B3 site, 27 September 2016; PCZL S.A. 9.2. 39 specimens B3 site, September 2018 PCZL S.A. 9.3. The remaining material is in the MCG collection. Most material fixed in ethanol 70% (including the holotype and paratypes), and some in ethanol 95 %. Description. Holotype complete, with eight thoracic and 28 abdominal chaetigers. Body length 2.8 mm, branchial crown 1 mm long, maximum body width 0.43 mm. Natural dark brown colouration presents especially in the thorax and highlighting the mid-dorsal faecal groove, and ventral shields. (Fig. 18A). Crown with five pairs of radioles with 14 pairs of pinnules arranged in two longitudinal rows alternating along the radiolar length. Gap between pairs decreasing along the radiole from the base to the distal end, with the first two basal pairs more separated from the others. Pinnules slender and elongated, showing a similar length (1/4 of the total radiolar length) with the distal pairs and the first two basal pairs slightly shorter. Tip of radioles elongated as long as pinnule length (measuring 1/4 of the total radiolar length) and with a blunt end (Fig. 18C). Radiolar skeleton with two rows of cells. Dorsal lips with pointed dorsal radiolar appendages clearly shorter and wider than the pinnule, being 1/7 of the total radiolar length. Anterior peristomial ring even in height all around and visible also ventrally. Posterior peristomial ring low. Ventral basal flanges high, extending as prominent ridge from base of ventralmost radioles, across anterior peristomial ring but appearing not connected (Fig. 18D, E). Peristomial eyes not visible. Pygidial eyes present, as clusters of brown spots on lateral margins of pygidium. Thorax longer than wide. First thoracic chaetiger bearing only 3 chaetae similar in shape to the thoracic superior chaetae. From the second to the eighth thoracic chaetiger, 6 uncini in each torus with well developed breast, large distance to main fang, with approximately four rows of long teeth above main fang, and short handles long 1/3 of the total uncinus’ length (0.30) (Fig. 19A). Companion chaetae with straight shaft and short mucro (Fig. 19B). Second to eighth thoracic chaetigers with 4 chaetae, of which one superior broadly hooded chaeta (Fig. 19D) and three paleate chaetae on each thoracic chaetiger, with short mucro (Fig. 19E). Five abdominal uncini with similar-sized small teeth above the main fang, higher than thoracic ones and with short handle; the uncini are also larger in height than the other species, as in A. vulcanoensis sp. nov. (Fig. 19C). Up to 3 abdominal broadly-hooded neurochaetae, becoming narrower and with a more geniculate appearance in the last segments (Fig. 19G, F). A pair of brown/red spermathechae present at the base of dorsal lips. Staining pattern. In both, thorax and abdomen stain only ventral shields overlapping the natural brown colouration. Colouration pattern wide on both thorax and abdomen following the shape of the segments, but not reaching the tori (Fig. 18B). Variation. Individuals always with 8 thoracic chaetigers and up to 28 abdominal chaetigers. Mean body length of 2.55 mm and mean crown length of 1.08 mm. Peristomial eyes visible only in few specimens. Up to 8 thoracic uncini and 6 abdominal one (Table 1). Remarks. The new taxon is very characteristic in its colouration, although variable in intensity among specimens, as well as for its very compact appearance. This dark brown colour pattern is quite unusual among Amphiglena species. Peristomial rings and basal ventral flanges are quite similar to A. cf. mediterranea, from which it is distinguished for the first peristomial ring visible also ventrally, for the staining pattern, for a more compact appearance with wider and lower segments, but especially for the short handle of thoracic uncini.Among the non Mediterranean species, the new taxon is similar to A. nishi Capa & Rouse, 2007 described from Japan, especially in the shape of peristomial rings and ventral basal flanges. This species is however a smaller taxon with only 4 radioles. Etymology. The species is named from the type locality, the Aeolian Archipelago (north Sicily) where the species was collected. Distribution and ecology. This species is one of the most abundant taxa of the benthic community associated to the brown macroalga Cystoseira brachycarpa, dominating the rocks around the Bottaro crater and the hydrothermal system around it (see Auriemma et al. 2019, for a description of the collection area). Its local distribution in the area and its relationship with another new congeneric species are discussed below., Published as part of Giangrande, Adriana, Putignano, Matteo, Licciano, Margherita & Gambi, Maria Cristina, 2021, The Pandora's box: Morphological diversity within the genus Amphiglena Claparède, 1864 (Sabellidae, Annelida) in the Mediterranean Sea, with description of nine new species, pp. 201-239 in Zootaxa 4949 (2) on pages 225-227, DOI: 10.11646/zootaxa.4949.2.1, http://zenodo.org/record/4636125, {"references":["Capa, M. & Rouse, G. W. (2007) Phylogenetic relationships within Amphiglena Claparede, 1864 (Polychaeta: Sabellidae), description of five new species from Australia, a new species from Japan, and comments on previously described species. Journal of Natural History, 41, 327 - 356. https: // doi. org / 10.1080 / 00222930701194938","Auriemma, R., De Vittor, C., Esposito, V., Gaglioti, M. & Gambi, M. C. (2019) Motile Fauna associated to Cystoseira brachycarpa along a gradient of Ocean Acidification at a vent system off Panarea (Aeolian Islands, Italy). Biologia Marina Mediterranea, 26 (1), 216 - 219."]}

Amphiglena pithecusensis sp. nov. (Figs 6, 7) Material examined. Holotype (MNCN 16.01 /18901): Italy: Lacco Ameno (Ischia), 40°45’24.38”N 13°53’6.26”E, June 2012, 2– 3 m depth, on hard bottoms covered by macroalgae, mainly the brown alga Halopteris scoparia. Paratypes: MNCN 16.01 /18902: 5 specimens from the same locality and date as the holotype, 13 specimens from the same site of the holotype; PCZL S.A. 3.1.; 5 specimens from S. Anna rocks (Ischia-Cartaromana Bay), 40°43’34.58”N 13°57’35.98”E, 26 August 2014. PCZL S.A. 3.2. Most material fixed in formalin 4% (including holotype and paratypes) and preserved in 70% ethanol, some material fixed in ethanol 95 %. Description. Holotype complete, with eight thoracic and 24 abdominal chaetigers. Body length 2.5 mm (branchial crown 1.5 mm); width 0.4 mm (Table 1). Body light brown coloured on ventral side and with a flattened abdomen (Fig. 6A). Crown with five pairs of radioles with 12 pairs of pinnules arranged in two longitudinal rows slightly alternating along the radiolar length. Gap between pinnules pairs decreasing along the radiole, with the first basal pair appearing slightly more separated from the others. Pinnules all of similar length, measuring about 1/4 of the total radiolar length, except first basal pair and the two distal pairs slightly shorter. Tip of radioles elongated, reaching almost 1/3 of the total radiolar length, thinning toward its blunt end (Fig. 6C). Anterior peristomial ring not visible. Posterior peristomial ring higher ventrally with a well separated ventral incision and margins with an inflated appearance (Fig. 6D, E), connected to ventral basal flanges extending as prominent ridges from the peristomial ring to the base of ventral-most radiole. Peristomial eyes brown. Dorsal lips measuring 1/5 of the radiolar length. Pygidial eyes present as small clusters of red spots on lateral margins of pygidium. Thorax longer than wide. First thoracic chaetiger bearing only 2 chaetae similar in shape to superior chaetae of the following chaetigers. From the second to the eighth thoracic chaetiger, 7 uncini in each torus, with a short handle approximately 1/4 of the total uncinus length (0.31), with approximately four rows of teeth above main fang, and with rounded and flattened breast (Fig. 7A). Companion chaetae present, with straight shaft and short mucro (Fig. 7B). Two superior broadly hooded chaetae (Fig. 7D); 3 inferior paleate chaetae with short mucro as long as the paleate region (Fig. 7E). Three abdominal uncini, with similar-sized small teeth above the main fang, with short-handle and appearing higher than long (Fig. 7C). Two abdominal broadly hooded chaetae, similar, but longer, to the thoracic paleate chaetae both in anterior and median abdominal segments (Fig. 7F, G). Spermathechae visible brown/red coloured. Staining pattern. In both thorax and abdomen stain only the ventral shields, with a very narrow pattern especially in the abdomen remaining poorly stained (Fig. 6B). Variation. Individuals with 8 thoracic chaetigers and up to 24 abdominal segments. Mean body length of 2.1 mm and mean crown length of 1.3 mm (Table 1). Crown asymmetrical in some specimens composed of 11 radioles (5 pairs +1). Remarks. Specimens similar in external morphology to A. aenariensis sp. nov. previously described, but distinguished from that species by having slightly longer handles of the thoracic uncini, although not as long as in A. cf mediterranea. Moreover, hooks are proportionately smaller. Other differences are in a different ratio between body and crown (Table 1), in the narrow paleate chaetae in the thorax and abdominal chaetae of the mid body chaetigers which in A. aenariensis appear more geniculate and longer. Differences also in the ventral shape of the posterior peristomial ring with slight inflated margin, and in the shorter dorsal lips, and the ventral shield stain in this taxon appears less intense and narrower especially in the abdomen. Finally, the space between the pinnules in the radioles appears wider than in A. aenariensis sp. nov.. Etymology. Named from type locality. Lacco Ameno represents the first site of settlement of the ancient Greek populations (Eubei) at Ischia in the 8 th century BC, who called the island Pithekoussai, or Pithecusae in ancient Latin, due to the production of the local clay pottery. Distribution and Ecology. This species belongs to a group of similar taxa that are abundant around the coast off the Ischia Island. This species is present all around Ischia on hard bottoms with different algal cover, as well as on Posidonia oceanica seagrass beds under “normal pH condition”, except at the San Pietro site, where a form similar to A. mediterranea is present.

Genus Amphiglena Claparède, 1864 Type species: Amphicora mediterranea Leydig, 1851, subsequent designation by Bush (1905). The following diagnosis is based on that by Fitzhugh, 1989, revised by Capa & Rouse (2007). Diagnosis: Small-sized sabellin species bearing 5 to 8 pairs of radioles; radiolar skeleton with two rows of cells. Palmate membrane and radiolar flanges absent. Dorsal lips with dorsal radiolar appendages; dorsal pinnular appendages absent. Ventral lips absent; parallel lamellae absent. Ventral basal flanges of branchial crown present, as a pair of thin, erect, membranous flanges extending from the base of radioles and posteriorly across the anterior peristomial ring to proximal region of ventral-most radioles. Peristomial ring generally divided by a mid-ventral incision. Anterior margin of anterior peristomial ring low, of equal height all around, but often not visible all around because thinner and fused to the posterior ring. Posterior peristomial ring longer than the anterior ring with anterior margin horizontal or prolonged ventrally on both sides of the mid-ventral incision. Posterior peristomial ring collar absent. Variable number of thoracic chaetigers. Superior thoracic notochaetae broadly-hooded. Inferior thoracic notochaetae paleate, arranged in single transverse row. A single transverse row of abdominal neurochaetae assumed to be anterior row (posterior row absent); composed of elongate, broadly hooded chaetae. Thoracic uncini with teeth above main fang of equal size; hood absent; breast well developed, expanded; handles of variable length. Companion chaetae with distal end slightly inflated, dentate and with a thin mucro extending from this. Abdominal uncini with main fang surmounted by teeth of equal size; breast well developed, handles very short. Abdominal chaetiger not numerous. Pygidial eyes present., Published as part of Giangrande, Adriana, Putignano, Matteo, Licciano, Margherita & Gambi, Maria Cristina, 2021, The Pandora's box: Morphological diversity within the genus Amphiglena Claparède, 1864 (Sabellidae, Annelida) in the Mediterranean Sea, with description of nine new species, pp. 201-239 in Zootaxa 4949 (2) on page 204, DOI: 10.11646/zootaxa.4949.2.1, http://zenodo.org/record/4636125, {"references":["Claparede, E. (1864) Glanures zootomique parmi les annelides de Port Vendres (Pyrenees Orientales). Memoires de la Societe de physique et d'histoire naturelle de Geneve, 17, 463 - 600. https: // doi. org / 10.5962 / bhl. title. 14827","Leydig, F. (1851). Anatomische Bemerkungen uber Carinaria, Firola und Amphicora. Zeitschrift fur wissenschaftliche Zoologie, 3, 325 - 332, pl. IX, figs. 4 - 7.","Fitzhugh, K. (1989) A systematic revision of the Sabellidae - Caobangiidae - Sabellongidae complex (Annelida: Polychaeta). Bulletin of the American Museum of Natural History, 192, 1 - 104.","Capa, M. & Rouse, G. W. (2007) Phylogenetic relationships within Amphiglena Claparede, 1864 (Polychaeta: Sabellidae), description of five new species from Australia, a new species from Japan, and comments on previously described species. Journal of Natural History, 41, 327 - 356. https: // doi. org / 10.1080 / 00222930701194938"]}

Amphiglena nisidensis sp. nov. ( Figs 8, 9) Material examined. Holotype (MNCN 16.01 /18903): Italy: Nisida Island (Naples), 40°47’31.52”N 14° 9’47.29”E, 14 November 2011; 2 m depth. Collected on hard bottom with algal cover, mainly Halopteris scoparia. Paratypes: MNCN 16.01 /18904: 6 specimens from the same locality and date as the holotype; 22 specimens from the same locality and date as the holotype PCZL S.A. 4.1. Most material fixed in formalin 4% (including holotype and paratypes) and preserved in ethanol 70%; some material fixed in ethanol 95 %. Description. Holotype complete with eight thoracic and 28 abdominal chaetigers. Body length 2.5 mm, with crown 1.8 mm long, and 0.4 mm wide. Body light brown coloured on ventral side and with flattened abdomen (Fig. 8A). Crown with five pairs of radioles with 12 pairs of pinnules of medium length each, arranged in two longitudinal rows with a small space gap between the pinnules of the same pair, and with space increasing at the base of the radiole. The pinnules appear longer in median position where they measure 1/4 of the total radiolar length, and becoming considerably shorter towards the end of the radiole. Tip of radiole long, slender and pointed (Fig. 8C). Dorsal lips measuring 1/5 of the total radiolar length.Anterior peristomial ring not visible. Posterior peristomial ring higher ventrally with a mid-ventral incision where low ventral basal flanges attach, extending as prominent ridges from base of ventral-most radioles (Fig. 8D, E). Small brown peristomial eyes present. Pygidial eyes present as clusters of red spots on lateral margins of pygidium. Thorax longer than wide. First thoracic chaetiger with only 3 chaetae similar in shape to the superior chaetae of the following chaetigers. From the second to the eighth thoracic chaetiger, 5 uncini on each torus. Thoracic uncini with rounded and flattened breast, with four rows of teeth above main fang, and with handles long approximately 1/3 of the total uncinus length (0.35) so considered between medium and short length (Fig. 9A). Companion chaetae present, with straight shaft and long mucro (Fig. 9B). Thoracic chaetae from second to eighth chaetigers, number 4, of which one superior broadly-hooded chaeta (Fig. 9D) and three paleate chaetae in inferior row with mucro long as the hood (Fig. 9E). Abdominal uncini in number of 3, with similar-sized small teeth above the main fang, higher than the thoracic one and with short handle (Fig. 9C). Three abdominal neurochaetae thin and broadly hooded, similar to paleate of the thorax but longer in the first abdominal segments (Fig. 9G) and becoming longer and more geniculate starting from mid abdomen (Fig. 9H). Spermathechae present brown/red coloured. Staining pattern. In both thorax and abdomen stain only ventral shields. Peristomium, thorax and abdomen showing an intense colouration in the central part, but with a pattern covering most of the segment width (Fig. 8B). Variation. Individuals have eight thoracic chaetigers and up to 31 abdominal chaetigers. Mean body length of 1.65 mm and mean crown length of 1.5 mm. (Table 1). Remarks. The material from Nisida is very similar morphologically to A. pithecusensis sp. nov. previously described. The specimens from Nisida, however, appeared highly flattened in the abdomen and with wider bands of stained tissue as wide as the thoracic segment. Moreover, specimens have a larger ratio between body and crown (Table 1), with a longer and slender tip of radioles and pinnules arranged in pairs, not alternating along the radiolar length. Thoracic uncini are also similar in the length of the handles but with a slender main fang. The main difference is, however in the shape of the ventral margin of the peristomial ring showing an incision without separated margins, and with a lower basal flange. Ventral peristomial ring appears similar to A. bondi Capa & Rouse, 2007, from which it is distinguished by the short handle of thoracic uncini, and by the number of radioles. Etymology. Named from type locality, the Island of Nisida, located between the Gulf of Naples and the Gulf of Pozzuoli. Distribution and Ecology. Distributed on hard bottoms with algal cover. This species belongs to the same group of similar taxa that includes specimens from Ischia vent and non-vent’s areas, except the San Pietro site.

Amphiglena vulcanoensis sp. nov. (Figs 16, 17) Material examined. Holotype: (MNCN 16.01 /18911): Italy: Vulcano Island-Baia di Levante vent system, 8 May 2013, 38°25’10.10”N 14°57’43.38”E; 1.5 m depth (Vizzini et al. 2017). Paratypes: MNCN 16.01 /18912: 3 specimens from same locality and date as the holotype; 49 specimens, all collected in the same locality and date as the holotype PCZL S.A. 8.1. Material fixed ethanol 95% (including holotype and paratypes). Description. Holotype complete, with eight thoracic and 32 abdominal chaetigers. Body length 4.2 mm, branchial crown 1.5 mm; maximum body width 0.5 mm, abdomen largely flattened. Yellow colouration presents especially in the thorax, highlighting the mid-dorsally faecal groove, and ventral shields (Fig. 16A). Crown with 7 pairs of radioles with 16 pairs of pinnules arranged in two longitudinal rows alternating along the radiolar length. The gap between pinnule pairs remaining constant along the radiole, with only the first basal pair more separated from the successive one. The pinnules show a variable length appearing very short and with a characteristic swell on the end, not observed in other species. The tip of radioles short and blunt (Fig. 16C). Dorsal lips with very long and rounded dorsal radiolar appendages, (1/3 of radiolar length). Radiolar skeleton with two rows of cells. Anterior peristomial ring not visible. Posterior peristomial ring low with two small ventral projections with low margin, ventral basal flanges thick and extending as prominent ridge from the base of the ventral-most radioles. Base of crown distinctly thick (Fig. 16D, E). Peristomial eye not visible. Pygidial eyes present as cluster of brown spots on lateral margins of pygidium. Thorax longer than wide. First thoracic chaetiger bearing only 3 chaetae similar in shape to the superior chaetae of the other thoracic segments. From the second to the eighth thoracic chaetiger, 7 uncini in each torus, with approximately five rows of similar-sized small teeth above the main fang and well-developed breast, going beyond the main fang and with large distance above main fang. Medium-short handles long around 1/3 of the total uncinus length (0.35); the uncini are also larger in height than the other species (Fig. 17A). Companion chaetae present, with straight shaft and short mucro (Fig. 17B). Second to eighth thoracic chaetigers with 5 chaetae of which one superior chaeta broadly hooded and four inferior paleate chaetae of two different typologies, one having a mucro long as the hood, the second showing a very short mucro and a reduced length (Fig. 17D, E, H). Four abdominal uncini on each torus with 4 teeth, uncini higher than longer and with a medium handle (Fig. 17C). Four broadly hooded abdominal neurochaetae similar to the inferior paleate chaetae both in the first and median abdominal segments, but the last becoming longer (Fig. 17F, G). Spermathechae light brown/coloured. Staining pattern. In both thorax and abdomen stain only ventral shields, intensely coloured on the peristomial ring, and abdomen with a narrow stained string (Fig. 16B). Variation. Individuals always with 8 thoracic chaetigers and up to 32 abdominal chaetigers. Mean body length of 3.7 mm and mean crown length of 1.3 mm. Up to 10 thoracic uncini on each torus and 7 abdominal uncini (Table 1). Remarks. This is a species larger than the other congeneric species, with a compact appearance and with the largest number of radioles of all Mediterranean species, and non Mediterranean species. In this aspect, it resembles the Australian species A. magna Capa & Rouse, 2007 from which it is distinguished by the length of handles of thoracic uncini, but also by the ventral peristomial shape. This feature is similar to A. terebro Rouse, 1993, which is a smaller species with fewer radioles and 12 thoracic chaetigers. Etymology. The species is named from type locality, the Island of Vulcano (Aeolian Archipelago, north Sicily). Distribution and Ecology. The species up to date has been collected only in Baia di Levante hydrothermal vent’ system of Vulcano island. This vent’s system is unique since it is not only acidified due to CO 2 emissions from the primary vent source (approx. 300 m from the collection area), but has also some sulphur (H 2 S) and is enriched by metal ions (see Vizzini et al. 2017, and references herein for a description of the system and its benthic community). Amphiglena vulcanoensis sp. nov. was collected with a few other polychaetes, among which Platynereis cf. massiliensis Moquin-Tandon, 1869 was the dominant species (Waege et al. 2017, Vizzini et al. 2017)., Published as part of Giangrande, Adriana, Putignano, Matteo, Licciano, Margherita & Gambi, Maria Cristina, 2021, The Pandora's box: Morphological diversity within the genus Amphiglena Claparède, 1864 (Sabellidae, Annelida) in the Mediterranean Sea, with description of nine new species, pp. 201-239 in Zootaxa 4949 (2) on pages 222-224, DOI: 10.11646/zootaxa.4949.2.1, http://zenodo.org/record/4636125, {"references":["Vizzini, S., Martinez-Crego, B., Andolina, C., Massa-Gallucci, A., Connell, S. D. & Gambi, M. C. (2017) Ocean acidification as a driver of community simplification via the collapse of higher-order and rise of lower-order consumers. Scientific Report, 7, 4018. https: // doi. org / 10.1038 / s 41598 - 017 - 03802 - w","Capa, M. & Rouse, G. W. (2007) Phylogenetic relationships within Amphiglena Claparede, 1864 (Polychaeta: Sabellidae), description of five new species from Australia, a new species from Japan, and comments on previously described species. Journal of Natural History, 41, 327 - 356. https: // doi. org / 10.1080 / 00222930701194938","Rouse, G. W. (1993) Amphiglena terebro sp. nov. (Polychaeta: Sabellidae: Sabellinae) from eastern Australia; including a description of larval development and sperm ultrastructure. Ophelia, 37, 1 - 18. https: // doi. org / 10.1080 / 00785326.1993.10430373","Waege, J., Valvassori, G., Hardege, J. D., Shulze, A. & Gambi, M. C. (2017) The sibling polychaetes Platynereis dumerilii and Platynereis massiliensis in the Mediterranean Sea: are phylogeographic patterns related to exposure to ocean acidification? Marine Biology, 164 (10), 199. https: // doi. org / 10.1007 / s 00227 - 017 - 3222 - x"]}

Amphiglena messapica sp. nov. (Figs 12, 13) Material examined. Holotype (MNCN 16.01/18907): Italy: Santa Caterina-Torre Inserraglio (Apulian Coast, Ionian Sea), 40° 8’22.13”N 17°58’47.31”E, collected in 2002 from hard bottom at 1 m depth, covered by Halopteris sp. and Dictyota sp. Paratypes: MNCN 16.01 /18908: 7 specimens from the same locality and date as the holotype; 118 specimens all collected in the same locality and date as the holotype PCZL S.A. 6.1. Most material fixed in formalin 4% (including holotype and paratypes) and preserved in ethanol 70%; some material fixed in ethanol 95 %. Description. Holotype complete, with eight thoracic and 28 abdominal chaetigers. Body length 3 mm, branchial crown 1 mm; maximum body width 0.35 mm (Fig. 12A). Crown with five pairs of radioles with 11 pairs of pinnules arranged in two longitudinal rows not alternating along the radiolar length. Gap between pinnule pairs constant along the radiole. Pinnules quite short and with a similar length (1/4 of the total radiolar length), being shorter only in the first two basal pairs and in the last two distal pairs. Radiolar tip reaching between 1/3 and 1/4 of the total radiolar length and with a blunt tip (Fig. 12C). Radiolar skeleton with two rows of cells. Dorsal radiolar appendages long 1/3 of total radiolar length. Anterior peristomial ring not visible. Posterior peristomial ring short but oblique, appearing as having pointed margin (Fig. 12D, E). Ventral basal flanges high extending as prominent ridge from base of the ventralmost radioles across the anterior peristomial ring and highly connected with the peristomial ring (Fig. 12D, E). Peristomial eyes not visible. Pygidial eyes brown spots on lateral margins of pygidium. Thorax longer than wide. The first thoracic chaetiger bearing only 3 chaetae similar in shape to the superior thoracic chaetae. From the second to the eighth thoracic chaetiger, 6 uncini on each torus, with well-developed breast, large distance to main fang, and approximately four rows of long teeth above main fang, and medium handles, measuring more than 1/3 of the total uncinus length (0.43) so that the uncinus appears longer than higher (Fig. 13A). Companion chaetae present, with straight shaft and long mucro (Fig. 13B). From the second to the eighth thoracic chaetiger, 2 superior broadly hooded chaetae (Fig. 13D) and 4 paleate chaetae in inferior group with mucro long as the hood (Fig. 13E). Four abdominal uncini with similar-sized small teeth above main fang, longer than thoracic ones and with short handle (Fig. 13C). Spermathechae not visible. Up to 3 abdominal hooded neurochaetae with hood similar to the inferior chaetae in the first abdominal segments (Fig. 13F) becoming longer and more geniculate in the median abdominal segments (Fig. 13G). Staining pattern. In both thorax and abdomen stain only ventral shields with a large rectangular pattern in the thorax, and a double clear squared pattern on each abdominal segment (Fig. 12B). Variation. Individuals always with eight thoracic chaetigers and up to 28 abdominal chaetigers. Mean body length of 2.3 mm and mean crown length of 0.9 mm (Table 1). Remarks. Although being a compact form like the previous described species, this taxon is larger and with a longer appearance, especially in the abdominal chaetigers. The handles of the thoracic uncini, although having a similar length as A. cf. mediterranea, appear more pointed. Amphiglena messapica sp. nov. differs from this taxon especially in the shape of the peristomial ring which is ventrally higher and with more developed basal flanges, connected to the peristomial ring, so that it appears as pointed. The staining pattern is similar to A. aenariensis sp. nov., and to all the related taxa of the group from the Gulf of Naples. This species is distinguished from this group of taxa for the length of the handles of the thoracic uncini, and for the body/crown ratio, this last feature being similar to A. cf. mediterranea (Table 1). Among the non Mediterranean taxa, A. gracilis Capa & Rouse (2007) has the most similar ventral peristomial appearance, however, this species does not have the peristomial edge so connected to the ventral basal flanges, moreover, A. gracilis is a very thin species with only four pair of radioles, has a shorter handle of thoracic uncini, and a longer dorsal radiolar appendages. Lastly A. messapica sp. nov. is among the few Mediterranean species not showing an alternate arrangement of the pinnnule rows along the radiole. Etymology. The species was named from the “Messapi”, an ancient tribe inhabiting in pre-Roman time the Southern Apulia (Salento), where the species was collected. Distribution and ecology. The species is distributed on shallow and sheltered hard shallow substrates., Published as part of Giangrande, Adriana, Putignano, Matteo, Licciano, Margherita & Gambi, Maria Cristina, 2021, The Pandora's box: Morphological diversity within the genus Amphiglena Claparède, 1864 (Sabellidae, Annelida) in the Mediterranean Sea, with description of nine new species, pp. 201-239 in Zootaxa 4949 (2) on pages 217-218, DOI: 10.11646/zootaxa.4949.2.1, http://zenodo.org/record/4636125, {"references":["Capa, M. & Rouse, G. W. (2007) Phylogenetic relationships within Amphiglena Claparede, 1864 (Polychaeta: Sabellidae), description of five new species from Australia, a new species from Japan, and comments on previously described species. Journal of Natural History, 41, 327 - 356. https: // doi. org / 10.1080 / 00222930701194938"]}

Amphiglena gravinae sp. nov. (Figs 14, 15) Material examined. Holotype: (MNCN 16.01 /18909): Italy: Adriatic Sea, Brindisi, 40°38’53.39”N 18° 0’42.01”E, in 1985, 5 m depth, on corallinae algae. Paratypes: MNCN 16.01 /18910: 5 specimens from the same locality and date as the holotype; 296 specimens, all collected in the same locality and date as the holotype. PCZL S.A. 7.1. Material fixed in formalin 4% and preserved in ethanol 70 %. Description. Holotype complete with 8 thoracic and 22 abdominal chaetigers. Total body length 4 mm, crown 0.6 mm; maximum body width 0.3 mm (Fig. 14A). Crown holding five pairs of radioles with 11 pairs of short pinnules arranged in two alternating rows of similar length (between 1/5 and 1/4 of the total radiolar length. The gap between pairs remains quite constant along the radiole. First basal pair and last distal pair with pinnules shorter than that in the medial radioles. Elongated radiolar tip, reaching more than 1/3 of the total radiolar length and of uniform width, and with a blunt tip (Fig. 14C). Radiolar skeleton with two rows of cells. Dorsal lips with long and pointed dorsal radiolar appendages (1/3 of crown length). Anterior peristomial ring with similar height all around, visible also on ventral side. Posterior peristomial ring elongate and connected to high ventral basal flanges, which extends as prominent ridge from base of ventralmost radioles (Fig. 15D, E). Peristomial eyes not visible, pygidial eyes present, as very small spots on lateral margins of pygidium. Thorax longer than wide. The first thoracic chaetiger bearing only 3 chaetae similar in shape to the thoracic superior chaetae. From the second to the eighth thoracic chaetiger, 6 uncini on each torus with well-developed breast, and approximately four rows of similar teeth above main fang, large space to main fang, handle elongated, substantially longer than 1/3 of the total uncinus length and considered long handles (0.52) (Fig. 15A). Companion chaetae present, with straight shaft and long mucro (Fig. 15B). Second to eighth thoracic chaetigers with 4 chaetae, one superior broadly hooded chaeta (Fig. 15D), and three inferior paleate chaetae with a short mucro, long slightly less than the hood (Fig. 15E). Four abdominal uncini on each torus with similar-sized small teeth above the main fang and medium handle (Fig. 15C). Four abdominal broadly hooded neurochaetae, but with a very large hood similar to the thoracic paleate chaetae, even if longer. The shape of the chaetae is similar along the abdominal segments even if in the last segments they become longer and with a more geniculate appearance (Fig. 15G, F). Pair of light spermathechae present at the base of dorsal lips. Staining pattern. In both thorax and abdomen stain only the ventral shields, with a pale colouration, abdomen with a double rectangle in each segment (Fig. 14B). Variation. Individuals always with 8 thoracic chaetigers and up to 30 abdominal chaetigers. Up to 7 thoracic uncini. Mean body length of 2.6 mm and mean crown length of 0.9 mm (Table 1). Remarks. This new taxon has a more elongate appearance than other species in the genus, including the peristomial rings, and the base of the crown appearing sometimes bearing a high basal web, and making difficult to see the separation between the peristomial ring and the base of the crown. In this feature it is very similar to A. panareensis sp. nov., which is the other elongate Mediterranean species, described in the present paper. The two species, however show a different development of both first and second peristomial rings. Among the non Mediterranean species, high developed ventral flanges are present also in A. lenae Capa & Rouse, 2007, but this is a thin and more compact species, with smaller radiolar appendages. The staining patter is similar to A. messapica sp. nov., even if it appears narrower and more elongated following the elongated shape of the segments. It is distinguished from this species by the shape of the peristomial rings and for the abdominal chaetae, maintaining a paleate appearance long all the abdomen. This feature is present also in A. nisidensis sp. nov., and in A. vulcanoensis sp. nov. where, however, chaetae are less broadly-hooded. Lastly, A. gravinae has the thoracic uncini with the longest handle compared to all the Mediterranean species here described, although very similar in shape to A. messapica sp. nov. Etymology. The species is named after the Dr. Maria Flavia Gravina who collected the material, in honor of her valuable contribution to the knowledge of the taxonomy and ecology of polychaetes, as well as for our estimation, long-lasting friendship and collaboration. Distribution and Ecology. The species was collected in a polluted and stressed area, characterized by the presence of high sedimentation rate, and in the vicinity of a power plant.